Question

What is the correct sequence of the complementary strand for the given portion of a DNA molecule:- 5' - G A C G T A C -3' ?

• A. 3' - T T G C A T G - 5'
• B. 3' - C T G C A T C - 5'
• C. 3' - C T G C A T G - 5'
• D. 3' - C T G T A T G - 5'

Hint:

Pair A with T and G with C, and write the new strand in the opposite direction.

Answer 1

The Correct Option is C

Step 1: Plan:
Write the partner of each base under it, keeping the strands antiparallel so the left end of the given strand is its $5'$ end and the partner's left end is its $3'$ end.

Step 2: Pairing table:
G-C, A-T, C-G, G-C, T-A, A-T, C-G. Reading the bases in that order gives CTGCATG.
So the partner strand is $3'$-CTGCATG-$5'$. Only option C matches every pair.

Final Answer:
The complementary strand is $3'$-CTGCATG-$5'$, option (C). \[ \boxed{3'\text{-CTGCATG-}5'} \]